It has been known for a great many years that effective exercises for maintenance of physical fitness can be carried out in a limited space by muscular exertion against a restraining device. In particular, exercise of the leg muscles, as well as of the heart, lungs, back, and even arm muscles is achieved by "running in place", especially if forward pressure is exerted against a restraining device.
The restraining device for running in place generally takes the form of a broad belt or band passing around the front of the waist or of the hips of the user, and is anchored to a fixed object behind the user.